Ethanol and alcohol mixtures including ethanol may be used as fuels and fuel additives in place of petroleum-based products such as gasoline. Such use of alcohols can reduce the need to import petroleum. In addition, the substitution of alcohols for petroleum-based fuels and fuel additives can be particularly environmentally friendly when the alcohols are produced from feedstocks other than fossil fuels.
One synthetic route to alcohols is through catalytic processes for the conversion of syngas to alcohols. Syngas (or synthesis gas) is a mixture of monoxide (CO) and hydrogen (H2). Generally, syngas may be produced from any carbonaceous material. In particular, biomass such as, for example, agricultural wastes, forest products, grasses, and other cellulosic material may be converted to syngas.
There exist a variety of conversion technologies to turn these feedstocks into syngas. Conversion approaches can utilize a combination of one or more steps comprising gasification, pyrolysis, steam reforming, and/or partial oxidation of a carbonaceous material.
Since the 1920s it has been known that mixtures of methanol and other alcohols can be obtained by reacting syngas over certain catalysts (Forzatti et al., Cat. Rev.—Sci. and Eng. 33(1-2), 109-168, 1991). Fischer and Tropsch observed around the same time that hydrocarbon-synthesis catalysts produced linear alcohols as byproducts (Fischer and Tropsch, Brennst.-Chem. 7:97, 1926).
However, improved methods and apparatus to convert syngas into alcohols, such as ethanol, are currently needed.